invalid_factory_name_not_a_class

The name of a factory constructor must be the same as the name of the immediately enclosing class.

The analyzer produces this diagnostic when the name of a factory constructor isn't the same as the name of the surrounding class.

The following code produces this diagnostic because the name of the factory constructor (A) isn't the same as the surrounding class (C):

class A {}

class C {
  factory A() => throw 0;
}

If the factory returns an instance of the surrounding class, and you intend it to be an unnamed factory constructor, then rename the factory:

class A {}

class C {
  factory C() => throw 0;
}

If the factory returns an instance of the surrounding class, and you intend it to be a named factory constructor, then prefix the name of the factory constructor with the name of the surrounding class:

class A {}

class C {
  factory C.a() => throw 0;
}

If the factory returns an instance of a different class, then move the factory to that class:

class A {
  factory A() => throw 0;
}

class C {}

If the factory returns an instance of a different class, but you can't modify that class or don't want to move the factory, then convert it to be a static method:

class A {}

class C {
  static A a() => throw 0;
}

Unless stated otherwise, the documentation on this site reflects Dart 3.8.0. Page last updated on 2025-05-08. View source or report an issue.